Relationship between autonomic dysfunction and BP variability in subjects with diabetes mellitus.

Autonomic vagal heart rate (HR) control, office BP and ambulatory BP were examined in 54 diabetic subjects, aged 63 +/- 6 years. Sixteen subjects were insulin-dependent. The HR response to deep breathing (the bradypnoea test) was used to evaluate the vagal HR control, and ambulatory BP was determined by the Spacelabs 5200 system (one determination every 15 minutes, for 24 hours). Twenty-seven subjects had normal office BP (SBP < or = 140 mmHg and DBP < or = 90 mmHg), seven had established hypertension (SBP > or = 160 mmHg and DBP > or = 95 mmHg) and 30 were borderline hypertensives. Over the total group, office systolic/diastolic BP (mean +/- SD) was 142 +/- 20/85 +/- 10 mmg. Systolic/diastolic ambulatory BP was 123 +/- 13/77 +/- 10 mmHg and ambulatory HR was 70 +/- 8 beats/min. Because of the small age range of our subjects, the HR score was not correlated with age (r = 0.19, NS). The HR score was not correlated with the levels of office and ambulatory pressures. In contrast, it was significantly correlated with the variability of ambulatory SBP, whether the variability was defined by the pressure standard deviation, or by the ratio SD/mean value (r = 0.40, P = 0.005 and r = 0.33, P < 0.017, respectively). We suggest that an impairment of the autonomic control in diabetics might induce an increase in variability of SBP. BP variability might play a role in the cardiovascular complications observed in diabetics.